Fig. 2

Examples of NMs as building blocks of NIs. 1: Picture of a sea cucumber changing its stiffness from a soft (a) to a stiff (b) configuration. (c) Laser-micromachined cortical probe with a parylene C capping layer fabricated with a 12.2% v/v poly (vinyl acetate) (PVAc)/cellulose nanofiber nanocomposite used as a mechanically adaptive substrate (thickness: 60 μm). Photographs of an electrode during its insertion into the brain of a rat showing correct penetration of the nanocomposite electrode (d) and the buckling effect of a neat polymer electrode used as a control (e), demonstrating that cellulose nanofibers can effectively act as stiffness-adapting elements (Reproduced and adapted with permission. [Harris et al. 2011d,e; Capadona et al. 2012 a,b,c] Copyright 2011, IOP Publishing; Copyright 2012, Springer). 2: (a) Scheme of the fabrication steps of a bacterial cellulose-based NI. (b) Photograph of a bacterial cellulose-based device connected to a recording system. (c) Images showing the extreme flexibility of a bacterial cellulose-based NI, which remains intact after repeated twisting and untwisting (100 times) (Reproduced and adapted with permission from [Yang et al. 2018] Copyright 2018, ACS Publications). 3: (a) Schematic illustration describing the use of silk/fibroin as a substrate for the nontransient neural interface for the peripheral nerve and for the cortex. (b) Silk-based NI wrapped around a silicon tube. (c) Picture showing the electrode silk substrate and superstrate with embedded conductive lines. (d) Silk-based NI wrapped around the sciatic nerve (right) to record the electrical signal at two different points (left). (e) Comparative cortical activity recorded by silk-based cortical electrodes prior to (left) and post (right) ischemia induction (Reproduced with permission from [Patil et al. 2020a, b] © 2020 John Wiley & Sons, Inc.)